Bland said:
I use the Sanyo Eneloop as well and they've been great. They take hours to recharge but no biggie as you can get a 1,000 shots per charge. I think I paid around $30 for 4 of them with charger.

Thanks Bland, unfortunately I need about 40 of them to power my various bits of kit, so it's not going to be a cheap purchase. This is why I was asking for anyone's personal experience on whether it is worth paying the extra for the 2500 mAh verities? Charging time is not a deal breaker for me, as I always carry spares on a shoot, and so can charge at my leisure when I get back.

adamz said:
I use a lot of the regular ones and don't have any problems with them whatsover; as for PW neither minittl or flex accepts AA

By regular ones you mean 2000 mAh ? Why do you say PW Mini TT1's & Flex TT5's don't work with AA's? That's all they take?

Most of the info has been covered here already but I've spent a bit of time experimenting with rechargeables etc for high power flashlights so i'd like to offer this as a quick summary

For fastest recharge / maximum flashes in flashguns etc (high drain equipment) use high power NiMH cells.They can hold the most energy.
But - high power NiMH discharge quickly by themselves when sat on a shelf - so to get their full capacity charge them the night before you use them. If you leave them in your bag for 3 months they'll probably come out empty - don't use these for an emergency light you leave in your car :-)

As has already been said, rechargeables only give 1.2volts compared to 1.5 volts for primary cells, but the voltage of any battery drops the more current you draw from it. This effect is much more severe in primary batteries.
End result, rechargeables are better at driving anything that needs a lot of current like a flashgun or when you push transmit on your walkie-talkie.

The new "low self discharge" NiMH cells that have appeared on the market in the last year or so don't have as much capacity (around 2000mAH) as the standard NiMH cells but are still great at driving high drain equipment. Their advantage is that they keep their charge much better . They are sold "ready to use" from the packet and will still have ~85% of a full charge after sitting for 12 months. I use these for the spares in my kit so that I don't have to cycle them every week to keep them full.

I've used Duracell brand and "GePe ReCyko" brand in the UK and both are good. Both makers produce a range of batteries so check you're selecting the variety you want. Eneloops are a best seller worldwide - they wouldn't be if they weren't a decent product.

I suggest buying from name brands because they have more reputation to lose so quality control is likely to be good.

For low consumption devices and kit that needs the full 1.5 volts, I think that Energiser primary (i.e. disposable) lithium batteries - the silver and blue ones - are expensive but worth it. They have much higher capacity than normal alkaline cells and a massive shelf life. These are excellent in GPS receivers and the like because you don't have to replace or recharge them often and the long life means you rarely need to carry spares. They also keep working in the cold while alkaline cells in particular do not.

The best charger you can buy for AA and AAA cells is the Powerex / Maha Wizard One charger. Expensive but it charges from one to four cells individually controlled by computer - lets you discharge each cell to empty, fast or slow charge it to full, measures the capacity of each cell so you can match them into sets, etc etc. This keeps your cells in great condition.

My last point is about care and maintenance -

Memory effect is more myth than real and doesn't apply to NiMH or Lithium rechargeables so there's no reason not to recharge a half used set of cells.

What kills rechargeable batteries is running the pack absolutely empty. Whatever it says on the label, each cell will have a different capacity - sometime very different. When you run a set of batteries right down, one of them will reach empty first. The remaining cells then continue to push current through the empty cell "over discharging" it. This causes the weak cell to heat up and heat eventually this causes the cell to fail. The answer is to swap out the batteries as soon as you notice any real drop in performance as this is an indicator that the weakest cell has reached empty. This applies to cordless power tools even more than cells used in photography.

A great advantage of the wizard one charger is that you can see the real capacity of each cell so you can match your rechargeables into sets that will all empty at about the same time.

The second common way of killing NiMH cells is to use a fast charger that doesn't turn off when the cell is full. As soon as a cell is full, the extra energy has nowhere to go so starts heating up the cell. Regular overcharging kills cells so I recommend buying a good charger otherwise the life of your cells will be much less than the lifetime promised by the manufacturer.

Fortunately the lithium rechargeable packs used in cameras, laptops, etc include electronic circuits to protect them from overcharging, over discharge and the other abuse that can cause them to fail dramatically. No special advise is needed except to note that that a lithium pack can be damaged if left in a discharged condition for a long time so best to recharge after use, and to remind you that lithium is not something to be messed with so stick to the approved charger unless you know exactly what you're doing :-)

Another good charger is the La Crosse BC-700 (edit: I guess I've got the BC-900). I've been using mine for a couple of years and although the adapter connection has been kind of spotty for a couple of months, the charger has been great (I need to open it up and solder that connection—this is not unusual for anything I leave out where my two young boys can play with it).

I kind of feel like I've mentioned it before on this thread but I'm too lazy to check.

Thanks Sideways, thanks Jonny and everyone else who has contributed. I have found a company on Amazon selling 40 2000mAh Eneloops for £60, seems to be the best price I can find, also I currently have an 8 AA charger so might buy another to speed up the process of charging them all after a big shoot. Some Korean company is selling a 20/50/100 AA charger on eBay, that would certainly finish the job in double quick time!

I'll second jonnyapple's recommendation of the La Crosse charger. I have the BC-700 and have been really happy with it. Biggest advantage is that it is a four channel charger so each battery is charged independently of the others. This comes in really handy when recharging the 5 batteries for the flashgun. Recharge four and then recharge the fifth. No needing another dead battery to be able to charge an odd number.

I have a MAHA MH-C9000 Advanced Battery Charger sold by thomasdistributing dot com, fantastic chargers they bring dead batteries to life, independent channels and all the works. For batteries I use Sanyo Eneloop 2000 mAh for AA and 800 mAh for AAA.